What is silicon nitride (SiN)?

Silicon nitride has the chemical formula Si3N4. It is a ceramic material of high strength, wear resistance, and inherent lubricity. It is a atomic crystal and resists oxidation in high temperatures. It is also resistant to the impact of both cold and heat. It won’t be damaged if you heat it to over 1000degC and cool it quickly, then heat it rapidly. The excellent properties of silicon nitride are the reason why it is used in many mechanical components, such as bearings and turbine blades. It can also be used to produce mechanical seal rings, permanent moldings, etc. When silicon nitride is used for the heating surfaces on engine components, it can not only improve the engine’s quality, but also fuel efficiency and thermal efficiency. China, Japan, the United States and other countries are developing such engines.

How to prepare silicon nitride

It is widely used in China. The method is simple and inexpensive. Metal silicon powder is heated with nitrogen or ammonia in an atmosphere. The metal silicon and nitrogen source directly react and form silicon nitride.

This method is cost-effective and requires little equipment. The metal silica powder nitridation is an exothermic process. The nearby metal silicon will melt if heat is not released at the right time. The result of the nitriding. The nitriding process is controlled by the temperature, speed and particle size. The synthesised silicon nitride comes in a block-like shape. The silicon nitride must be prepared by other methods such as ball milling, which are not very efficient and introduce impurities into the process.

In the presence of high-temperature nitrogen, SiO2 is reduced with carbon powder. SiO2 is reduced to gas-phase SiO first, and the gas-phase SiO reacts to nitrogen in atmosphere to produce silicon nitride.

Thermal decomposition uses SiCl4 to react at low temperatures with ammonia gas in order to obtain solid imino or amino silicon. These two silicides may be decomposed under high temperatures in order to obtain nitride Silicon. This method can be used to prepare large quantities of high purity silicon nitride in a very short time. This method can produce silicon nitride that is high in purity and has uniform particle sizes. This method has been the most popular method for commercial production high-purity, high-quality silicon powder.

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